Conventional test tube racks typically consist of a horizontal support plate for supporting the bottom of the test tubes and spaced apart above the support plate one or two horizontal apertured plates for receiving the test tubes and holding them in upright position which plates are secured to upright sidewalls. Such a test tube rack is disclosed, e.g. in U.S. Pat. No. 1,188,146. Another less common type of holder, for test tubes or similar elongated receptacles is in the form of wire baskets wherein the horizontal plates and sidewalls are replaced by a welded wire structure. Different materials including wood, steel, aluminum and plastic have been used in the manufacture of test tube racks. Yet the basic shape has remained the same, including a horizontal support on which the test tubes are deposited at the same level.
These test tube racks have various disadvantages which are particularly troublesome in the case of test tube racks for holding a larger number of test tubes, e.g. up to 72 tubes, arranged in several, e.g. up to 6, rows, as are used in large hospital and research laboratories for carrying out a series of analytical tests.
Thus, accurately and speedy pipetting into the tubes in rear rows is difficult without removing the tubes from the rack. This is particulary the case where small amounts have to be pipetted into the tubes at the bottom, e.g. by means of micropipettors with tips. Removing a test tube from a plurality of test tubes standing upright next to each other only relatively narrowly spaced apart is time consuming and not very convenient.
Also, when one or more reagents are to be pipetted into each of a larger number of test tubes deposited in a conventional test tube rack, one does not become readily aware when a tube has inadvertently been left out because it is difficult to see whether indeed all tubes have received the respective reagents without carefully checking each tube, e.g. by removing same from the rack.